Process of concentration of solutes



Jan. 12, 1965 A. F. REID PRocEss oF CONCENTRATION oF sow'rss 2 Sheets-Sheet l Filed May 7, 1959 Jan. 12, 1965 A. F. REID PRocEss oF CONCENTRATION oF soLuTEs 2 Sheets-Sheet 2 Filed May 7, 1959 "lul- Shuk INVEN TOR. ue/y Pavo Array/ver United States Patent() 3,165,384 PROCESS OF CONCENTRATION F SOLUTES Allen F. Reid, The University of Texas, 5323 Harry Hines Blvd., Dallas 3S, Tex. Filed May 7, 1959, Ser. No. 811,732 2 Claims. (Cl. 23a-310) This invention relates to the change in the relative concentration of one or more of the constituents of a liquid composition, such as a liquid solution.

, The object of the invention is to provide a process subjecting the solution to a series of treatments to increase the proportionate amount of one or more constituents of a separate portion of the solution while at the same time decreasing the concentration of similar constituents in another separate portion of the solution.

, Another object of the invention is to provide the transfer of a constituent of a solution from one phase to another phase by direct interface contact of the two phases.

A further object of the invention is to provide a method employing a series of operations with a recycling and 1 a reconditioning of process materials to produce the desited products in an energy-conserving and economic manner. f

A further object is the production of industrial, agricultural or household water from sea or brackish water where economy of production is intimately tied tothe energy requirements.

Other and further objects and advantages will become apparent from the following description taken in conby the addition of a third constituent in a concentrated form in one stage and a diluted form'in the other stage. The third constituent is then removed from the separate portions or phases to form a solution depleted of `the r'st solute A and another'separate solution enriched with y 'the first solute A.

The mechanisms of the process are the treating of the original solution with said third constituent, the introduction of the treated solution into a concentration cell in which the concentration of the original solute Ais either increased or decreased in one portion of the solution followed by the removal of that changed portion of the solution from the cell and treatment of the removed portion in order to re-establish therein the original conditions for the process.

The other portion of the cell solution, in which the 1' 'concentration of the solute is changed in an opposite direction tothe first other portion of the solution, is also removed from the cell and treated to re-establish the Aoriginal conditions for the process.

As a result of these operations a solution withan intermediate concentration of solute A has been processed to yield one portion of a more highly concentrated solution of A and another portion of a solution depleted in A. For simplicity, the terms solute and solvent are intended to include` generally the constituentsk of a col- `loidal suspension as well as those of a true solution. Where further concentration or depletion is desired beyond any stage, the products of the concentration procedure described may be further treated by the same 3,165,384 Patented Jan. 12, 1965 "ice process. One of these methods effecting further relative concentration or depletion is the placing of each separation stage contiguous to the next stage with the same type ot countercurrent operation used in a rectifying system. Another method is a recycling arrangement such as that described in my U.S. Patent No. 2,772,953, dated December 4, 1956.

One method for obtaining the desired change in concentration of the solute in a solution relies on the change in solubility of a solute A when another diierent solute is introduced into the solution. When a solute A is soluble in each of two different solvents which are in separate phases communicating with each other, the solute A will distribute itself in such a manner as to favor dissolution and relative concentration in the solvent in which it is more soluble. There are many instances in which the addition of a second solute to a solution containing A will decrease the solubility of such a solute A to an extent depending on the concentration of the second or added solute. Where upon adding this second solute to the solution, there is a division of the solution into two phases with different concentrations of the second solute, then there Vwill be a redistribution of the original solute A such that its concentration per unit volume of the solvent will be higher in one phaseV than in the other. Upon separation of these phases and the subsequent removal of the second solute, one of the resulting portions of the solvent or solution will have a higher concentration of the original solute A and one will have a lower concentration of A. The following example serves to illustrate the method.

Example I Phenol was added to a 0.500 molal solution of sodium chloride in water. It dissolved and the solution was allowed to come to equilibrium at 22.5 C. The solution separated into two phases, the top phase containing 5.9% phenol and the bottom phase 69.8% phenol. The phases were separatedand the phenol was extracted from each phase with chloroform. The sodium chloride in the ex` tracted top phase water-was, 0.586. molal; the sodium chloride in the extracted bottom phase water Was 0.116 molal. The phenol andchloroform could be separated byA conventional distillation methods so that bothwould be again available for further process operation.

An alternative method for the removal of phenol from solution was demonstrated by placing .a solution identical with the top phase in contact with one-fifth its weight of -nely divided activated charcoal at 25 C. for 10 minutes. At Ithe end of that period 92.4% of the phenol was sorbed to the charcoal. Further sorption could be carried out to bring thephenol concentration in the solution to as low a value `fas desired. .The phenol may be recovered from the sorber by conventional methods such as leaching with an appropriate solvent with subsequent distillation of the solvent. This variationof means of removal of an added solute may bel used when appropriatein any method set forth in which treatment of the solution is by the addition of another solute.

Another examples Yserves to illustrate some differences in operation: Y p

\ f- Example II Tetronic *702, a polyoxyethylene compound of molecular weight between 2500 and 3000 made byy the Wyan- .dotte Chemicals Corporation, Wyandotte, Michigan, and herein designated as Y, was added to 0.050-molal solution of sodium chloride in water. It dissolvedY and the solution was allowed to come to equilibrium at 48 C. The .solution had separated into two phases, the top yphase containing 1% Y and the bottom contaiing 49% Y. The Vsodium chloride distributed itself between these two phases so that the concentration in the top phase was 1.26 times the concentration for'f the same amount of Water in the bottom phase. The two phases were separated. The bottom phase was heated to. 66 C. Most of the Y separated ina slightly hydrated condition (17% water) leaving a supernatant sodium chlorides-solution containing only v1% Y which was 15% less concentrated in sodium chloride than the solution in the upperv phase at 48 C. A small amount of salt was still dissolvedin `the hydrated Y, but the Y in this form could practically be used over and over again in similar operations for the changing of sodium` chloride concentration in water. When necessary, the small amount of Y leftV in the separated solutions described could be removed by conven- Twenty-eight milliliters phenylhydrazine were added to 35 milliliters 0.50 molal solution of sodlum chloride l phases of the solution arepin liquid to liquid interface com in water.- It dissolved and the solution was allowed to come to equilibrium at 24 C.' The solution separated into two phases, the top phase containing 8.4% phenyli' hydrazine and the bottom phase containing 56.0% phenylhydrazine. The sodium chloride distributed itself between these two phases so that its concentrationin the top phase was 1.42 timesY its concentration for the same amount of water in the bottom phase. The two phases were separated `and` were cooled Ito 10 C. Solid hydrated phenylhydrazine separated out Yfrom each phase leaving asupernatant sodium chloride solution in each case containing only 5.4% phenylhydrazine. The phen-v ylhydrazine in this form could practically be used over and over again in similar operations for the changing of sodium chloride concentration in water.

A system wasV set up to vary the concentration of sodium chloride in water with phenol las the added solute. A glass tube 48 -centimeters long and 18 millimeters in diameter was packed with 3fm" diameter ,pyrex helices for 40 cm. of the tubes length. Ar phase solution -G was introduced at the top and a phase solution H was introduced at the bottom of the tube.. Both'soluti'ons ran the length of the tube but in a countercurrent direction Y When necessary, the phenylhydrazine left in the separated solutions l to each other, each leaving the tube at the opposite yend from which it started. This system wasy operated for ninety minutes to developa relatively steady state after which production samples were taken .for`analysis., On entering the concentration vcell Vthe solution G was 0.067 molal to sodium chloride land 72.3% phenol;;and the solution H was 0.015 molal to sodium chloride andV 6.1%

phenol.

70.7% phenol; and the solutionH was 0.076 molal to sodium chloride and 6,3% phenol. The operation of thisl 'sequencev of concentration andv depletion may `be traced by starting Iatthe end at which the solution G is intro- On discharge from theconcentration cell the. solution G Was 0.015 molal to sodium` chloride and f duced and the solution H is discharged. Y Solution G loses f some of. its sodium chloride through the liquid-liquid interface and continues on its yway-down `the tube. Solu- `tion H flows in .the opposite' direction where it is continuously acquiring an increased concentration of sodium chloride from Vthe solution G, finally leaving the system withV a concentration of sodium chloride higher than the original concentration of sodium chloride in the solution G. In the meantime solution G llows toward its exit be- Corning progressively less and `less concentrated in sodium chloride' until it leavesk the system with a concentration of sodium chloride as low as the original concentration of sodium chloride in H.

A small amount of the depleted phase VsolutionV G may be removed andthe phenol extracted from the solution to form a waterproduct depleted of sodium chloride and phenol; and the remainder of the depleted phase Vsolution G m-ay be reintroduced into the system as Vphase solution H. 'As an overall consequence of this method of voper-ation withrefiux at o ne end the original solution is separated into two portions, one with a higher and one with a lower concentration vof sodium chloride. When desired, the adaptation to a systemwith reflux and production at both ends canbemade using standard engineering principles'.A y

Aynr embodiment of one of the methods performed in accordance with the invention is diagrammatically illustrated in FIG. 1. In the concentration cell 1 Ythe two tact `for the transference of the solute from one phase to the other, using engineering practices standard to liquidliquid extraction. The units 3b, 4, 5, 6, 7,8, 9, 10 and 14 are liquid-liquid extractorsfor removing solute from the solutions. Stills 2 and 11 are provided for the recovery of solvents and reservoirs 12, 13 and.15 are provided for storing solvents. Thesolvent S and solute X are the primary components of Athe-solution Sotreated in the process. Inthe process this solution S0 is divided into two .separate portions, S1 and SI2.` The concentration of the solute X in the portion S41 is lincreased and is substantially reduced inthe portionSz. Thersolute Z is added to the solvent S lfor forming solvent S -into separate phases. SolventL extracts the solute Z from the solution. Solvent T extracts L from thevsolvent S. The solute Z and the solvents L and T are used in connection with the processing o-f both portions S1 and'Sz of the solution.

The process diagrammed in .F.IG. 1 shows the solution S0, composed of 'the solvent S `and-*the solute X, fed to the extractor 14. A solution of sfolvent L with solute Z dissolved therein is fed `to the extractor 14 from the reservoir 15. The solute Z is transferred to the solution S0. The solutionfSo comprises solvents, solute X and solute Z is fedto an intermediate portion of the phase H of the v cell-1 to mix with al solution comprising solvent S, solute X and solute Z. This mixture forms a dilute solution of Z in S. As the solutionA fed from extractor 4 progresses from the point of feed vfrom-the extractor 4,. the concentration of the solute X increases by transference of the solute X from the phase G atthe liquid-liquid interface. Thertransferencre of the solute X continues to the solution mixture as it progresses to the discharge to the unit 3a. The concentrated solution rof-solute X ing-solvent S is divided to forma por-tion recycled to the' cell 1 and a por- .tionSb The portion S1 is comprised primarily. of solvent S, solutes X 'l and Z which are-discharged from 3a. The 4other part fis delivered to the extractor 3b where radditional :solute Z lis added'from the still 2 to produce a high concentration of the Ysolute Z toform-the phase G. The solute Z may be supplied from the, still 2 Yas a concentrated solute in the solventL. The stripped solvent L is then rjed to the. reservoir 15.. Alternatively, the extractor -3bmay `be omitted and pure solute Z may be dissolved in the' solution. The phasefG is fed to the `concentration cell 1 and passes down through .the cell in liquid to liquid contact with the phase H.Y As it passes throughk the cell 1, the phase Gk becomesdepleted of the Vsolute X andjs discharged into Vthe liquid-liquid extractor 4 as a solution'c'omprising primarily the solvent S, solute `Z and a depleted solute X. The solvent Lis fed `from the reservoir 15 to the extractor 4'. The solute Z'is removed from the phase -G and discharged to the still 2. The solution S2 comprising primarily solvent S, solute Z and depleted solute X is discharged from extractor 4 in two directions. From the extractor 4 a portion of the solution S2 is fed to the concentration cell 1. The other portion of the solution S2 is then fed to the liquid-liquid extractors 6l and 8 in which the solvent L removes the last traces of the solute Z. The pure solvent L is fed from the reservoir 12 to the extractor 8 where it removes the solute Z. The solution of L and Z is then transferred to the reservoir 13 from which L is fed to extractor 6 to remove the solute Z. The solvent L becomes further concentrated with solute Z and is discharged to reservoir 15.

The solution S2 is discharged from the extractor 8 and comprises primarily solvents S and L and depleted solute X. In the extractor 10 solvent T is fed to the extractor 10 and removes the solvent L from the solution S2 and the combination of solvents L and T is discharged and fed to the still 11 where the solvents L and T are separated and the solvent L is discharged to the reservoir 12. The solution S2 discharged from the extractor 1t) comprises the solvent S with a perceptively small amount of the solute X. The solvent L containing the solute Z is fed to the still 2 whereL and Z are separated or Z concentrated in L land the pure solvent L is returned to the reservo-ir 12 andthe solute Z is delivered to the extractor 3b to dissolve in the solution to for-m the phase G as previously described.

The solution S1, comprising primarily solvent S, concentrated solute X`and solute Z, is delivered to the extractors 5 and 7 for the removal of the solute Z by solvent L. The pure solvent L is delivered to the extractor 7 from the reservoir 12. A combination of the solvent L with extracted solute Z is delivered to the reservoir 13 and in turn the solvent L with solute Z is delivered to extractor 5 for removal of solvent Z and discharged to the reservoir 15. The solution S1 discharged from the extractor 7 comprises primarily the solvent S, solvent L and solute X. The solvent T supplied from the still 11 removes the solvent L from the solution and the solution of solvents L and T is returned to the still 11 and separa-ted. The pure solvent L is returned tothe reservoir 12. The solution S1 is discharged from the extractor 9 and comprises primarily the solvent S and a concentrated solute X. Thus, the solution S of solvent S and solute X is divided into a solution S1 having a high concentration of solute X in the solvent S and a solution S2 comprising the solvent S with a small amount of solute X.

The reservoir 12 stores pure solvent L which is received from the stills 2 and 11. This pure solvent L is fed to the extractors 7 and 8. The reservoir 13 receives solvent L from the extractors 7 and 8. The solvent L contains solute Z. The reservoir 13 receives solvent L from the extractor 14. This solvent received from the extractor 14 is depleted in the solute Z. The solvent L with solute Z is supplied to the extractors and 6. However, the concentration of the solute Z in the solutions S1 and S2 is great enough so that the solvent L removes the solute Z from the solutions S1 and S2. The discharge of the extractors 5 and 6 is stored in the reservoir 15 along with the discharge of the extractor 3b. The solvent L discharged Iby the extractor 3b contains Z. The solvent L containing solute Z of the reservoir 15 is fed to the extractor 14 to provide the solution S0 with the solute Z to form the phase H for the concentra-tion cell 1. The solvent L and the solute Z are also fed to the extractor 4. However, since the solution S1 is high in Z there is a transference of the solute Z to the solvent L. The solvent L with a concentrated Z is then discharged to the still 2 where either a Separately pure solvent L and solvent Z are formed, or a pure L and a solvent L highly concentrated in the solute Z.

A specific embodiment of the above process is diagrammatically illustrated in FIG. 2. In this embodiment a concentration cell 21 circulates two phases of .a solution in opposite directions. A solution of `sodium chloride in water is fed to an intermediate stage of the cell 21 and circulated upwardly to increase in concentration in sodium chloride. A concentrated solution is fed into the mixing and dissolving cell 2,2. Phenol is added to the concentrated solution from .the still 34 and the precipitation cell 23. The phase of phenol and salt solution is fed to the concentration cell 21 and flows downward to discharge into the precipitation cell 23. Before the phenol is mixed with the concentrated salt solution .a portion ofthe salt solution is separated and discharged from the dissolving and mixing cell to the extractor 24. In the cell 21 the phase with the high concentration of dissolved phenol is in liquid to liquid interface contact with the rising phase of the salt solution. The sodium chloride is transferred from the downward flowing phase to the upward iiowing solution so that the downward flowing solution is depleted of sodium chloride. In the precipitation cell 23 phenol is precipitated out by cooling, leaving a salt solution depleted in sodium chloride with a low concentration of phenol. A portion of this solution is relluxed to the cell 21 to circulate up through the cell and mix with .the feed of salt solution from the feed reservoir 33. As the solution moves up through the cell, it increasesy inconcentration of sodium chloride from the downward descending phase. The other portion of` .the salt solution is delivered to the extractor 25. Further extraction of the phenol occurs in extractor 27 and a solution comprising the water depleted in sodium chloride and with a small amount of the carbon tetrachloride is delivered to the extractor 29 where .the carbon tetrachloride is removed by a solvent fed from the still 30. The solvent and the carbon tetrachloride are separated and the carbon tetrachloride is fed to the reservoir 31. The water is then discharged at 35 depleted in sodiurn chloride. The concentrated solution is treated in the extractors 24 and 26 to remove the phenol by carbon tetrachloride and the final traces of carbon terachloride are removed by the solvent from the still 30 to discharge a solution of concentrated sodium chloride in water at 36.

The carbon tetrachloride is delivered to the extractors 26 and 27 from the reservoir 31 and a discharge from the extractors 26 and 27 of phenol in carbon tetrachloride is delivered to the reservoir 32 which in turn delivers the carbon tetrachloride to the extractor 24. The combination of the carbon tetrachloride and phenol is delivered to the still 34 where the carbon tetrachloride is separated from the phenol and returned to the reservoir 3,1 and the phenol is delivered to the cell 22 as previously described.

F or every tive pounds of purified water processed about one pound of carbon tetrachloride mustv be distilled and about forty pounds of phenol must be precipitated by cooling and redissolved with added heat. The energyexpenditure required for this is lapproximately twenty percent of that required for conventional distillation in the production of the same amount of relatively salt-free water. With standard engineering practice much of this energy used in conventional distillation may be recovered, but with `available techniques it is to be expected that a large fraction ofthe energy used in the process of this invention may be recovered or reutilized.

A wide range of substances may be separated, or may be concentrated or depleted in solution by the above process. While specic examples have been illustrated, there are other systems for obtaining concentration changes for a collection of other solutes, solvents, temperatures, separators, or other methods of recycling. A range in the degree of concentration is also possible by changes in these variables when more than lone solute is present in the same solution.

Principles of separation may -be extended to each solute individually. It is thereby evident that changes in concentration of the individual solutes may be at diierent rates so that the ratios of concentration of these solutes may Vbe changed in the operation. This lis tantamount to relative separation of multiple constituents of a solution. A Several methods of the process may be combined in obvious ways or the methods may be combined with methods of other processes, all in conformance with the vsteps as explained above, and it will `be understood that various modifications canbe made without departing from the principles of the invention as vrset Afor-th in the appended claims.

I claim: f

1. A process for increasing the concentrationy of va solute content "inV one portion of a solution Whiley decreasing the concentration in another portion of the solution comprising circulating different phases -of a solution of va salt in opposite directions'f-in liquid Yinterface contact, vone .phase moving in one direction being supplied from a salt solution feed reservoir and the other second phase being supplied from an intermediate mixing and dissolving cell forming an organic and salt solution from addition of an organic compound to salt solution discharge from said'rst phase, said organic and salt solution passing as said opposite flow in liquid interface contact with the first phase of the salt solutionso that `salt solute is transferred to the first phase from said opposite flow and there '-isI a supply of relatively concentrated salt solutionto said mixing and dissolving cell and a relatively depleted salt Y solution comprising vcirculating diferentrphases of a solution `of .a sodium chloridein'opposite directions in liquid interface contact, one phase moving inone :direction being supplied from a sodium chloridek solution feed reservoir and the. other `second phase being supplied rornlan intersolution is maintained in .an outilow from said second phase. n Y

2. A process for increasing .the concentration of a mediate vmixing and dissolving cell forming ank organic Vand sodium chloride solution from `addition of an organic compound to Ysodium chloride solution discharge from `said first phase, said organicA andk sodium chloride solution passing as said opposite flow in liquid yinterface contact with the first phase ofthe sodium chloride solution so that sodium chloride solute. is transferred to the first' phase from said opposite flow and there 'is a supply of relatively concentrated sodium chloride solution to said mixing and dissolving cell and a relatively depleted sodium chloride.solutionisrnaintained.in an outflow fron'rsaid second phase. d

References @neutri theme ofi'this patent UNITEDSTATES PATENTS n p 2,900,223 cunninghamcg-; Aug.18,1959

OTHER REFERENCES a I Y.

Osterhautet al.: Science, volume 87,193.8, page430. Perry: Chemical Engineers Handbook, McGraw-Hill Publ. Co., 3rd edition, pages 714-752.` 

1. A PROCESS FOR INCREASING THE CONCENTRATION OF A SOLUTE CONTENT IN ONE PORTION OF A SOLUTION WHILE DECREASING THE CONCENTRATION IN ANOTHER PORTION OF THE SOLUTION COMPRISING CIRCULATING DIFFERENT PHASES OF A SOLUTION OF A SALT IN OPPOSITE DIRECTIONS IN LIUQID INTERFACE CONTACT, ONE PHASE MOVING IN ONE DIRECTION BEING SUPPLIED FROM A SALT SOLUTION FEED RESERVOIR AND THEOTHER SECOND PHASE BEING SUPPLIED FROM AN INTERMEDIATE MIXING AND DISSOLVING CELL FORMING AN ORGANIC AND SALT SOLUTION FROM ADDITION OF AN ORGANIC COMPOUND TO SALT SOLUTION DISCHARGE FROM SAID FIRST PHASE, SAID ORGANIC AND SALT SOLUTION PASSING AS SAID OPPOSITE FLOW IN LIQUID INTERFACE CONTACT WITH THE FIRST PHASE OF THE SALT SOLUTION SO THAT SALT SOLUTE IS TRANSFERRED TO THE FIRST PHASE FROM SAID OPPOSITE FLOW AND THERE IS A SUPPLY OF RELATIVELY CONCENTRATED SALT SOLUTION TO SAID MIXING AND DISSOLVING CELL AND A RELATIVELY DEPLETED SALT SOLUTION IS MAINTAINED IN AN OUTFLOW FROM SAID SECOND PHASE. 